The present invention relates to a method of treating a material such as a compound to remove and typically recover an oil from the material. The method of the invention is particularly suitable for recovering hydrocarbons from a mixture of hydrocarbons and aqueous liquids. In certain aspects, the invention can also be useful to recover oil from a mixture of materials containing solids (for example sand, glass, and metal pieces), liquids (for example fluid phase hydrocarbons, with aqueous phases containing water) and gases. In certain examples, the method of the invention relates to the recovery of oily fractions from waste material. For example, the removal or recovery of production fluids emanating from the well, or drilling mud added to the well, from drill cuttings recovered from oil and gas wells, typically but not exclusively generated by drilling and intervention operations in the well.
The removal or recovery of oily fractions from materials such as waste products is useful in the processing of waste generated by oil and gas well drilling. When an oil or gas well is drilled into a formation containing valuable hydrocarbons to be recovered, the drilling process generates drill cuttings (small chips of rock etc.) which are washed back to the surface and recovered from the well by the circulation of drilling mud in the well. In addition to washing the drill cuttings back to the surface, drilling mud (also called drilling fluid) is used to cool the drill bit and to resist blow outs during the drilling operation. The drill cuttings recovered at the surface are usually contaminated by hydrocarbons from the reservoir, which permeate the rock that was drilled in order to form the bore hole, and also by the drilling mud that is pumped down the hole in order to wash the cuttings out of the well. The contamination of the cuttings by the drilling mud and the hydrocarbons that permeate the cuttings currently present challenges for the operator, because environmental concerns dictate that the hydrocarbons contaminating the cuttings must be removed or reduced below the threshold before the cuttings can be safely disposed of. In addition, efficiency savings can be made by recycling the used drilling mud for subsequent use in future cycles, and by recovering the hydrocarbons on the drill cuttings for export from the well with the other valuable production fluids. Therefore, it is useful to be able to separate and typically recover the oily materials contaminating the waste drill cuttings before disposal of the cuttings.
Various methods are known for the removal of oily contaminants from drill cuttings. The following previous publications are useful for understanding the invention: US 2004/0144405; U.S. Pat. Nos. 6,485,631; 5,724,751; 4,869,810; 5,607,558; 6,485,631; and EP 0781313. The disclosure of these earlier publications is incorporated herein by reference. Typically the prior methods of separating hydrocarbons from the waste material involves heating the waste in the chamber of a rotary mill to evaporate the various fractions from the cuttings as gasses, and to separate the hydrocarbons from the mixture of vapours by distillation. Typically it is desirable to evaporate the hydrocarbons at temperatures lower than their atmospheric boiling points to avoid changing the molecular characteristics or “cracking” the hydrocarbons, so that more of the valuable longer chain hydrocarbons recovered from the distillation process can be exported from the well along with the other valuable production fluids for downstream processing and refining.